Have you tried shuttleworth? It is between Bedford and Biggleswade and you have the option of marrying in the manor house (it is very grand!) Or in the swiss gardens there. It is a beautiful venue & if I wasn't having a church wedding (2 miles from shuttleworth) then I would have probably got married there.
Good luck with your search & all the planning for your big day
I've looked at Tudor Barn in Burnham, a lovely out of the way venue with good access to motorways and excellent staff. I've also booked the Bucks violinist and pianist Simon Jordan to play for me and the Bucks photographer David Bostock.